Do you do any actual ab/core work? Since your abs are visible, that means your body fat is fairly low, you don't need to lose much more weight. Depends on how visible you want them. For men, the upper abs become visible at 12% bodyfat. To see the lower abs, you'll need to get below 10%. It will also depend on exactly where and how you store fat at the waist.

My lower abs are not visible at all but the upper abs are visible. At the moment i have a 4 pack with not much of a line down the middle